Thermostatic switch



May 3,- 1938. M, GUETT THERMOSTAT SWITCH Filed April 27, 1936 Tij. l.

I A ll.

INVENTOR MONROE GUETT BY HIS ATTORNEYS Patented May .3, 1938 THERMOSTATIC SWITCH Monroe Guett, Hartford, Conn., assignor to The Arrow-Harts; 'Hegeman, Electric Company, Hartford, Conn., a corporation of Connecticut Application April 2'1, 1936, Serial No. 76,692 i 12 Claims.

1 electric switch of the above type in which more positive snapping action of the contacts is accomplished upon operation of the device with the use of less bimetallic material than heretofore.

Another object of my invention is to provide an electric switch of the above type with simpler, more positive and more reliable means for adjusting the setting atwhich the device will operate.

Another object of my invention is to provide a switch .,of the above type with adjusting means which is operable by manual shifting of a lever and without the necessity of deformation of any part.

' Another object of my invention is to provide an electric switch of the above type with adjusting means which is capable of making finer adjustments with greater accuracy than heretofore.

' Other objects and advantages of my invention will become apparent as it is described in connection with the accompanying drawing.

, In the drawing- Figure l is an elevation view of a thermostatically operated electric switch embodying the principles of my invention.

35 Figure 2 is a plan view of the switch shown in Figure 1.

Figure 3 is a vertical section view taken along the line 3-3 of Figures 1 and 2.

Figure 4 is a plan view of -a fragment of the construction shown in Figures 1 and 2, illustrating the adjusting means in a different position than in Figure 2.

Figure 5 is an exploded view showing in perspective the parts of the adjusting mechanism 0 of my improved thermostatic switch.

The invention will be described as applied to a device for controlling the temperature in an electrically heated hot water tank.

Referring to the drawing, the parts of the invention are mounted upon a circular metallic body or mounting disc Ill. One end of a metal tube I2 is concentrically secured in a circular aperture in the center of the mounting disc III. In the other end of the tube l2 a metallic plug I4 is secured in any suitable fashion such as by a set screw, not shown; This plug has a diametrical recess l6 therein on opposite sides of which are two other deeper parallel recesses in which are mounted respectively the edge of a bimetallic strip l8 and a metal mounting plate 20. Another shorter bimetallic strip 22 is mounted upon plate 20 in any suitable fashion, such for example as by riveting. The bimetallic strip l8 extends upwardly and out through the upper end of the tube and has mounted upon its upper end a contact carrying plate 24 of approximately the same width as the bimetallic strip l8 and being in extension beyond the end of that bimetallic strip. A contact 26 is mounted upon the plate 24 but insulated therefrom in any suitable fashion as by insulating discs 28. A contact 30 similar to contact 26. engages with contact 26'and is in substantial alignment therewith. This contact 30 is mounted upon amounting plate 32 similar to the mounting plate 24 and the contact 30 is insulated from its carrying plate 32 by insulating discs 34 similar to the discs 28. The contact carrying plate 32 is mounted upon the upper end of a rigid strip of metal 36 while the lower end of the strip 36 is secured in a suitable fashion preferably by riveting to the upper end of the bimetallic strip 22. The metallic strip 36 is of substantial length and extends from the outside of the upper end of the tube l2 well down into the tube past the middle. Thus the bimetallic strip 22 may be short and is considerably less than half the length of the bimetallic strip IS. The tube l2 has sections cut out of its sides providing openings iii in diametrically opposite positions to provide for the passage through the tube in lateral direction of water or other fluid medium to the temperature of which the bimetallic ele'- ments are to respond.

As in prior devices the bimetallic elements are designed to bend in the same direction in response to a change in the temperature of the water and to cause the contacts to move in unison as the bimetal bends. Thus, the contacts remain engaged until a predetermined temperature is reached. At that point the contacts will snap apart under the influence of snap mechanism as will now be described.

In order to accomplish engagement and disengagement of the contacts with a snap the lower end of the contapt carrying plate 32 and the upper end of the plate 36 are bifurcated providing an aperture 40 in which a shortstrut 42 may move. This strut is provided with knife edges at its upper and lower ends, the upper edge engaging in a groove in the edge of the contact carrying while the lower edge of the strut engages with a transverse groove in the face of a stiff metallic diametrically positioned leaf spring 44, the latter groove being adjacent the inner end of this leaf spring. 1. The leaf spring 44 is mounted by means of a screw 46 which passes freely through its outer end and through a collar 48 and through an irregularly shaped adjusting plate 5|] (see Fig. 5) and threading into a sliding plate 52.

Theadjustment plate 50'is secured upon a sliding plate 52 having parallel straight edges which are adapted to slide along the side edges of a radial groove 54 cut in the upper face of the mounting disc ID. The adjusting plate 50 is secured upon this 'sliding plate 52 by means of the screw 46, the end of which takes into a threaded aperture 56 in the sliding plate 52. The adjusting plate 50 is further secured to the sliding p1ate52, adjustably, by means of a screw 58 passing through a curved slot 60 in the adjusting plate 50 and taking into a threaded aperture 62 in the sliding plate 52, this threaded aperture 62 being spaced from the aperture 56. The depth of the radial-channel 54 is preferably made of approximately the thickness of the sliding plate 52 so that when the adjustment plate 50 is secured upon the sliding plate the adjustment plate will lie flush upon the surface of the mounting disc i0 and at the same time will be flush with the surface of the sliding plate 52. The adjustment afforded by the arrangement just described may be considered as a primary adjustment as will hereinafter more fully appear during the description of secondary adjusting means now to be described.

Secondary adjusting means is provided for the purpose of making adjustments by hand without surface of the mounting disc l0 for the pivoted the necessity of use of tools and for the purpose of permitting the user to set the device for operation at various temperatures within a limited ia'nge as the requirements of the particular installation may dictate.

It will be noted from inspection of Figures 2, 4 and 5 that the adjustment plate 50 has a portion extending laterally beyond the radial channel 54 and sliding plate 52, over the surface of the mounting disc 50. Upwardly from and secured in this projecting portion there extends a pin i0. This pin 10 fits within a curved slot 12 in an adjusting lever 14 of irregular shape as may be noted in Figures 2, 4 and 5. This adjusting lever has a handle portion '56 extending beyond the periphery of the mounting disc 50. The adjusting lever 14 is pivotaliy mounted upon a pin 18 passing through a mounting bracket 80. One end of this mounting bracket is offset from the other so that when one end is placed upon the surface of the mounting disc i0 and secured thereon by a screw 82, the other end will be raised above the surface of the mounting disc It) to provide room between the bracket and the end of the adjusting lever 14, and also for a spacingwasher 84.

The center of curvature of the slot 12 in the adjusting lever 14 is offset from the axis of the pivot pin I8 so that as the adjusting lever I4 is moved about its pivot 18 the edges of the slot I2 will produce a camming action on the pin I0 tending to move the adjustment plate 50. Due to the fact that the adjustment plate 50 is secured-upon the sliding plate 20 in a position of permanent primary adjustment, the sliding plate 52 and adjustment plate 50 will move as 2,116,394 plate 32 between\ the bifurcations of that plate a unit in normal operation of the adjustment mechanism. Thus the camming action of the adjustment lever I4 causes the sliding plate 52 to move in the groove 54. This movement causes similar rectilinear movement of the switch spring 44 and shifts the lower knife edge pivot of the strut 42 toward and away from the surface of I 26and 30 to separate with a greater or lesser amount'of movement of the bimetallic elements i8 and 22. I

Due to the provision of the types of primary and secondary adjustment described, it is possible to adjust the device within a wider range and with a considerably greater accuracy than heretofore has beenpossible. The primary adjustment makes it possible to set the device roughly at the temperature at which it is desired to have the device operate. Then the finer manual adjustment by means of the adjustment lever 14 may be made.

Another-advantage is the ease of calibration and of original setting of the device. Scale divisions maybe marked on the mounting disc Ill and the hand lever. 12 set at the center and the primary adjustment -varied until the device operates at the setting desired for the central division.

It.has been found that the provision' of the short metallic strip 22 in lieu of a metallic strip extending all the way up to the contact carrier 32 not only reduces the cost of the device, but also provides a snapping action which is superior to that of prior constructions because the resistance to flexing of the composite support (20, 22, 36, 32) of the contact 30 is due only to the stiffness of the short bimetal strip 22, which is less than that of a full length strip, such as M. Hence as the over-center position is reached only the stiffnessKof the strip 22 need be overcome in order for the contact 30 to be able to snap away from 26.

Many changes within the scope of my invention will occur to those skilled in the art, therefore I do not limit myself to the specific embodiment of the invention as described.

i; In a thermostatic switch, a pair of engageable contacts, means flexing in response to predetermined temperature conditions for mounting at least one of said contacts, over-center snapping means for accomplishing separation and reengagement of said contacts-with a snap, in combination with a plural-part slidable unit, means for varying the relative positions of the parts of said unit to ailord primary adjustment of the setting of said over-center means, a manually operable member for auxiliary adjustment of said setting, and means between said unit and manual member exerting a camming actionto move said unit in response to movements of said manual member.

2, In a thermostatic switch, a pair of engageable contacts, means flexing in response to predetermined temperature conditions for mounting at least one of said contacts, over-center snapping means for accomplishing separation and reengagement of said contacts with a snap, in combination with means for adjusting the setting of said over-center means comprising a slidable plate, an adjustment plate adjustably mounted on said slidable plate for movement as a unit with said slidable plate, a pivoted lever operable by hand, and means between said lever and plate exerting a camming action to move said plate in response to movements of said lever.

3. In a. thermostatic switch, a pair of engageable contacts, means flexing in response to predetermined temperature conditions for mounting at least one of said contacts, over-center snapping means for accomplishing separation and reengagement of'said contacts with a snap, in combination with means for adjusting the seri'ing'of said over-center means comprising a' slidaole plate, an adjustment plate, means providing pivotal adjustment between said slidable plate and said adjustment plate, a manually operable pivoted lever, a pin and slot connection between said lever and adjustment plate exerting a camming action for moving said plate in response to movements of said lever.

A. In a thermostatic switch, a pair of engageable contacts, bimetallic means on which one of said contacts is mounted, composite mounting means on which said other contact is mounted including a short section of bimetal, over-center snapping means for separating said contacts with a snap upon predetermined movement of said bimetallic means and said composite means, said bimetallic means being constructed and arranged to urge said composite means in a direction to cause said snapping means to move over-center, in combination with means for adjusting the setting of said over-center means comprising a sliding plate, a manually operable member, and

means transmitting the motion of said manually operable member to said sliding plate by a camming action.

5. In a thermostatic switch, a pair of engageable contacts, bimetallic means on which one of said contacts is mounted, composite mounting means on which said other contact is mounted including a short section of bimetal, over-center snapping means for separating said contacts with a snap upon predetermined movement of said blmetallic means and said composite means, said bimetallic means being constructed and arranged to urge said composite means in a direction to cause said snapping means to'move over-center, in combination with means for adjusting the setting of said over-center means comprising a sliding plate, a manually operable member, and pin and slot connecting means transmitting the motion of said manually operable member to said sliding plate by a cammlng action.

6. In a thermostatic switch, a pair of engageable contacts, bimetallic means on which one of said contacts is mounted, composite mounting means on which said other contact is mounted including a short section of bimetal, over-center snapping means for separating said contacts with a snap upon predetermined movement of said bimetallic means and said composite means, said bimetallic means being constructed and arranged to urge said composite meansin a direction to cause said snapping means to move over-center, in combination with means for adjusting the setting of said over-center means comprising a sliding plate. a primary adjustment plate adjustably mounted on said sliding plate, a manually operable member providing a secondary adjustment of said sliding plate. and means transmitting the motion of said manually operable member to said adjustment plate by a camming action.

'7. In a thermostatic switch, a pair of engageable contacts, bimetallic means on which one of said contacts is mounted, composite mounting means on which said other contact is mounted including a short section of bimetal, over-center snapping means for separating said contacts with a snap upon predetermined movement of said bimetallic means and said composite means, said bimetallic means being constructed and arranged to urge said composite means in a direction to cause said snapping means to move over-center, in combination with means for adjusting the setting of said over-center means comprising a sliding plate, a primary adjustment plate adjustably mounted on said sliding plate, a manually operable member providing a secondary adjustment of said sliding plate, and means including a pin and slot connection for transmitting the motion of said manually operable member to said adjustment plate by a camming action.

8. In a thermostatic switch, a pair of engageable contacts, hert responsive means for mounting said contacts and causing their engagement and disengagement, and over-center snapping means for causing said contacts to be engaged and disengaged with a snap, said heat responsive means comprising a bimetallic strip of sufficient length and stiffness to ensure over-center movement of said snapping means,'and a composite member including a short section of bimetal of less stiffness than said bimetallic strip whereby the resistance to said over-center movement is minimized, in combination with means for adjusting the settingof said over-center means comprising a sliding plate, a manually operable member, and pin and slot connecting means transmitting the motion of said manually operable member to said sliding plate by a camming action.

9. In a thermostatic switch, a pair of engageable contacts, heat responsive means for mounting said contacts and causing their engagement and disengagement, and over-center snapping means for causing said contents to be engaged and disengaged with a snap, said heat responsive means comprising a bimetallic strip of sufficient length and stiffness to ensure over-center movement of said snapping means, and a composite member including a short section of bimetal of less stiffness than said bimetallic strip whereby the resistance to said over-center movement is minimized, in combination with means for adjusting the setting of said over-center means comprising a sliding plate, a primary adjustment plate adjustably mounted on said sliding plate, a manually operable member providing a secondary adjustment of said sliding plate, and means including a pin and slot connection for transmitting the motion of said manually operable member to said adjustment plate by a camming action.

10. In a thermostatic switch, a pair of engageable contacts, parallel mounting means for said contacts capable of flexing in response to predetermined temperature conditions, over-center snapping means for accomplishing separation and re-engagement of said contacts with a snap, in combination with means for adjusting the setting of said over-center means comprising a rectilinearly slidable plate, and adjustment plate adjustably mounted on said slidable plate for movement as a unit with said slidable plate, a

pivoted adjusting lever, a pin and slot connection between said lever and adjustment plate for moving said adjustment plate in response to movement of said lever.

11. In a thermostatic switch, a pair of engageable contacts, parallel mounting means for said (ill contacts capable of flexing in response to predetermined temperature conditions, over-center snapping means for accomplishing separation and reengagement of said contacts with a snap, in combination with means for adjusting the setting of said over-center means comprising a rectilinearly slidable plate, an adjustment plate, means providing pivotal adjustment between said slidable plate and said adjustment plate, a mannally operable lever having a pin and cam slot connection with said adjustment plate, whereby movement of said lever is transmitted to said slidable plate.

12. In a thermostatic switch, a pairof engageable contacts, parallel mounting means for said contacts capable of flexing in response to predetermined temperature conditions, over-center snapping means for accomplishing separation and re-engagement of said contacts with a snap, in combination with means for adjusting the setting of said over-center means comprising a rectilinearly slidable plate, a manually operable lever, a pin and slot connection between said lever and slidable plate for moving said plate in response to movement of said lever, and means for varying the position of said pin with relation to said plate to provide for a primary adjustment of the switch.

MONROE GUETI. 

